Changeable reactivity of ketyl radicals derived from 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones depending on electron transfer conditions employed

Abstract

Photoinduced electron transfer reaction of 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols.

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

“…Either external or internal bond cleavage of 8 generates the respective primary alkyl radical 9 or tertiary alkyl radical 10 . An equilibrium interconverting 9 and 10 through 8 [22–30] might occur (see below). A mechanism on the fragmentation of initially formed metal–organic complexes, giving β-ketoalkyl radicals [40], cyclopropoxy radicals [25,28,48–50], or β-metalated carbonyls [39], is still controversial [35–47].…”

“…1) that act as radical ion probes [20] and found that radical intermediates in their reaction pathways undergo efficient 5- exo hexenyl radical cyclization reactions [21], (Fig. 1) [22–30]. For example, PET reactions of probe I with amines were observed to produce a spirocyclic ketone product while its reduction reaction induced by samarium diiodide (SmI 2 ) gives rise to a cyclopropanol (left in Scheme 3) [22,24,27].…”

“…1) [22–30]. For example, PET reactions of probe I with amines were observed to produce a spirocyclic ketone product while its reduction reaction induced by samarium diiodide (SmI 2 ) gives rise to a cyclopropanol (left in Scheme 3) [22,24,27]. On the other hand, the same spirocyclic ketone is obtained in the 9,10-dicyanoanthracene (DCA) and biphenyl (BP) sensitized PET reaction of probe II , while reactions of this substrate with certain oxidants afford ring-expanded ketone and enone products (right in Scheme 3) [23,25–26 28–30].…”

Contrastive Photoreduction Pathways of Benzophenones Governed by Regiospecific Deprotonation of Imidazoline Radical Cations and Additive Effects

“…A preliminary observation that the irradiation of 1a with DMPBI predominantly produced 2a in aqueous MeCN was reported 4c…”

Photoinduced Electron Transfer Promoted Radical Ring Expansion and Cyclization Reactions of α-(ω-Carboxyalkyl) β-Keto Esters

“…Photoinduced electron transfer (PET) reactions that generate radical intermediates represent attractive alternative approaches for promoting Beckwith–Dowd ring expansion processes under mild and eco-friendly conditions. Although methods involving PET-promoted Beckwith–Dowd ring expansion reactions of halomethyl substituted benzocyclic ketones with amines and of α-bromomethyl β-keto esters by using a B 12 –TiO 2 hybrid catalyst have been described, both approaches require the use of haloketones as reactants and generate environmentally unfriendly hydrogen halides.…”